Automatic substation



Aug. 28, wz f 1,682,452

R. J. WENSLEY AUTOMATIC SUBSTATION Filed Sept. 23, 1924 5 Sheets-Sheet l O v 5 w N g N INVENTOR WlTNESSES:

gm mm .Aug. 28, 1928. 1,682,452

R. J. WENSLEY AUTOMATIC SUBS'IATION Filed Sept 23, 1924 5 Sheets-Sheet s R & 8

N N INVENTO TNESSES: Ray J [V /v4 BY a v I w f 4" m/ lA I NEY Patented Aug. 28, 1928.

UNIT ED STATES v 1582,45 2 PATENT QFFIC I ROY J. vvnns'nnr, or nnenw'oon; r nnnsrrvirnrn-i assrenen'ro washer-maven nnnornrc & manuracrn'n' ne coivrrrrnr, A oenron amrcnor earner-rulers.

AUTOMATIG Application file-'1 September tween two power circuits'in accordance with predetermined conditions.

Another object of my invention is to provide a: system, of the above-indicated character, in which-a control and indicating station is connected tothe translating station by only one wirev in addition to the conductors off? one otthe power circuits.

Another object ofmy invention is to provide means,- ina system of the above-indicated character, for regulating the field-magnet excitation of a translatingdevice to control one 'or another characteristic of the device de pending upon whether it is supplying energy to or receiving energy from its power circuit. In certain electrical, systems comprising both alternating-current and direct-current circuits, the alternating-current supply is the primary source of energy andthe direct-current energy is largely obtained from translating devices that are operated from the alternating-current system-. part of the' directcurrent energy, however, is usually supplied 7 from an independentsource,psuch as one or more steam-driven generators or the'jlike. Thus. it is almost always possible to obtain some direct-current energy even though the alternatingrc-urrent source may fail In large industrial and manufacturing plants, such, for example, as steel mills, certain essential apparatus is driven by alternating-current motors and it is of prime importance thatalterntit ing-current energy shall always be available for operating these 1110- tors as-the discontinuity of this service may often involve great losses and sometimes dam ger to operators. Therefore, 'I propose means embodied in my present invention, whereby an alternating-current system may receive energy through translating. devices from a directtcurrent system in emengenci is,

although the translating devices normally opcrate to receive energy from thealternatingcurrent system and to supplyencrgy to the sneer-Arron.

23,1924. Serial No; mazes,

ing-current dynamo-electric machine and a.

direct-current dynamo-electric:Ina-chine: Uni der normal conditionsof operation; the translating device is started and operatedfrom the alter-nsiting-current circuit in respouse to a demand tor load on the direct-cur-' rent circuit. The direct-current machine is then driven by the alternating curr'ent ma chine to supply energy to the direct-current circuit so long as suchenergy is required; TN hen the operation ofthe translating device is no longer required to supply energy to the direct-current circuit, its operation isauto matically stopped after apredeterminedin= tcrval of time.- v

I also providemeans that become operative n the-event that the voltage of the alternating-current circuit fails w-hethenor not the translating device is: opera ting-5 to cause" the direct-current machine to act asa motor-to drive thealternat'ingcurrent; machine which acts as a generator to supply energy to-the aflternating-current circuit and to maintaint-he voltage thereof at its normal value. In the event that the voltage of the a lternating-current circuit fails,;W-henthe translating device direct-currentcircuit and the single control conductor device indicates whether" or not the translating device. operativeI-v connected to the system a.

e more than one translating device is used, it may indicate just how many of the translating devices are operatively connected to the system.

My invention will be more clearly understood by reference to the accompanying drawings, in which Figures 1, 2, 3 and 1-, when placed end to end, from left to right as enumerated, form a diagran'imatic representation of an electrical systenrin which my invention is embodied, and

Fig. 5 comprises adefinition of the symbols used and a list of certain of the apparatus shown in the previous figures of the drawings.

Referring to Figs. 1, 2,3 and 4 of the drawings, an' alternating-current circuit 1 and a direct-currentcircuit comprising conductors 2 and 3, are provided with an alternating-current dynamo-electric machine 4 and a direct-eurrentsdynamo-electric machine 5, respectively. The rotating members of these machines are mechanically connected to each other by means of a shaft 6 that 3'81- mits either machine to drive the other. The alternating-current machine 4 may be connected to the alternating-current circuit 1 through astart-ing circuit interrupter 7 and an auto-transformer 8 or directly through a running circuit interrupter 9. One terminal of the direct-current machine 5 is connected to the conductor 8 of the direct-current circuit through an interpole field-magnet winding 10 and a series field-magnet winding 11, and the other terminal of the. direct-current machine 5 is connected to the conductor 2 of the direct-current circuit through resistors 12, 13 and 14, series load relays 15, 1G and 17,0ircuit interrupters 18, 19, 20 and 21 and a shunt 22.-

Under'normal conditions, when the volt ages of both the alternating-current circuit and the direct-current circuit are near their normal values, the alternating-current machine 4 is automaticallystarted and operated as asynchronous motor to drive the directcurrent machine 5 as a generator to supply energy to the direct-current circuit. This operation is automatically initiated in response to a demand for energy on the directcurrent circuit and is automatically stopped when this demand for energy remains below a predetermined value for a predetermined interval of time. In the event, however, that the voltage of the alternating-current circuit 1 falls below a predetermined value, the direct-current machine 5 is operated as .itHlOtOI from the direct-current circuit to drive the alternating-current machine 4 as a generator to supply energy 'to the alternating-current circuit 1 until the normal source of alternating-current energy again becomes available to maintain the voltage of the circuit 1 at sub stantially its normal value. 7

If the voltage failure of the circuit 1 occurs while the alternating-current macnine 4 is operating as a motor to drive the directcurrent machine 5 as a generator, the direction of energy traversal of the m chines a and 5 will simply reverse to cause the machine 5 to operate as a motor and the machine 4 as a generator. If the voltage failure occurs while the machines 1 and 5 are at a stand-- be superimposed upon the automatic control of the translating apparatus, I provide a control and indicating equipment 23 comprising push-button switches 24 and 25, a single- 'iole double-throw knife switch 26 and an indicating device 27. The only electrical connections between the controland indicating equipment 23 and the apparatus in the translating station are made through the confl duc'tors 2 and 3 of the direct-current circuit and a single additional control conductor 28. When availability of both automatic and manual control of the translating apparatus is desired, the knife switch 26 is closed in its lower position, as indicated in the drawing. If it is then desired to start the operation of the translating apparatus when there is not a sullicicnt demand for energy on the directc-urrent circuit to effect automatic starting of the apparatus, the push-buttou 25 is depressed. In like manner, it it is desiredto stop theoperation of the apparatus immediately at any time while it is operating, the push-button 24 is depressed. If it is'desired to entirely preclude operation of the apparatus either in response to the vfunctioning of theautomatic equipment or in response to manual operation of the pusl'ibutton 25, the knife switch 26 is closed in its up er position. The indicating device 271's adapted to indicate when the translating device is operatively connected between the power circuits and, in the event that more than one trans lating apparatus is provided, this device indicates how. many of the apparatus are operatively connected between the power circuits.

It will be understood that the conductors 2 and 3 of the direct-current circuit are usu ally the conductorssof a nctworkwhich traverses all of an industrial or manufacturing plant and that therefore they are available for connectionv at an desired point within the plant. Consequently. the only separate conductor which must be installed to connect the remote control. and indicating quipment llll 1 Hts with t'he loca l controlling equipment of the translating devices is the control conduc- 1301" 28; v p i I t In describing the operation ot the elec-- trica't system embodying my invention, let it first be assumed that the dynamo-electric machines 4 and 5 are at astandstilland are disconnected from their-respective circuits. Upon a demand for energy upon the directcurrent system in excess of the capacity of the translating devices that are already supplying energy thereto, the voltage between the conductors 'Q 'and' 3 falls'to such a value that an underload relay 29, (illustrated in" circuit A, Fig; 3) permits its: switch 29l (circuit B2')' towopen' and: itsswitch 29-2 (circuit B) to close. The operating coilof atime-delay-relay 30- (circuit B) is'thereupon connected between: the conductors 2 and 3 of the direct-current circuit to energize the same. This circuit is completed because switch 31- -1 otan' over-speed device 31, switch 32- 1- of a lockout relay 32, switch 33 4 of an alternating-current thermal relay 33 switch292 of the undervoltage relay 29 and switch-34-1 of an auxiliary master relay 134,- are. closed: The time delay relay 3'0. theretone hegins to actuate its switch 30-1 (circuit B toward i-tslclosed position.

If the" low voltagie condition of the directcurrent circuitcontinue's for the interval of time in which the relay? 30 is adjusted to close-its switch 3l',.the operating coilof a master relay 35 (circuit is energized.

ananxiliaryswitch 9'-.1 of the running circonnects the operating: coil of the auxiliary master relay 34 (circuitD) between the-con? ductors 2 .and 3 of the -direct=current circuit through a resist0r'38. The operating. coiloti The: energizing circuit for the coil of relay 35 extendstrom conductor?:through switches 31.1' and 32 1, (circuit B .switch' 322 (circuit B5 )3 of the'l'ockout relay 32, switch 36.1 of a stopping relay 36, a; resistor 37, operating coil otrelay35, switcl'l' 30-1 and cuit interrupter 9 to conductor 3. I

The relay 35-tl1ereupon closes its switches 35--1, (circuitB--3) 35 -2 (circuit B--54)' and 353(ci-rci'rit Dy,and opens its switch 354 (circuit V21*) The switch 35-.2 so shunts the'switches'31'1 and 9-1asto main tain energi'zation'ofthe relay 35 after either or both of the S-WitCllBSi 30 -1 and 9- 1 are opened. The closing 01? the switch 35-3 a control relay 39. (circuit D1)=, to] be described later v is connected directly between. the conductors 2 and. 3 whenthe sw-itch353 is closed. The auxiliary master relay 34, Wh en energized,opens its switches 34- 1 (circuit B) and 3%2 (circuit.B52) and closes switches84-3 (.circuitC) and switch 34-4 (circuit AA)... r

The closing. of switch 344 -3 (circuit C) connects, an auxiliary conductor 2A,.to which a number of. control apparatus. to. be describedl-ater, are connected to the conductor 2 ofthedirect-current circuit. When the conductor 2A is energized from the conductor 2, another auxiliary control relay 4O (circuit 7, switch441' of a time-delay cut-off relay 44 (circuit G--1), and switch 40-1 of the,

relay 40 to conductor 8 of the direct-current circuit" 4 v iVhen-the operating coil of therelay 42 is thus energized, two switches 42-1 (circuit F) and 422 (circuit G) are closed thereby. The switch 42l so shunts the switch 71 ofthestarting circuit interrupter 7 as to maintain energization oh the coil of relay 42' after the circuit interrupter-7 is actuated to its closed position. The switch 42-2, when closed, connectsthe closing coilTA of the starting circuit interrupter 7 between the conductors 2 and 3 of the direct-current circuit to effect closing of the interri'ipter 7. At the same time that the closing coil 7A is energized, the operating coil otthe time-delay cut-ofi' relay 44 is also connected between the conductors 2 and 3*. This circuit extends through switch 422 (circuit G) and an auxiliary switch 561 of a running circuit interrupter control relay 56 (circuit L) to be described later. After a predetermined interval of time, the time-dclayrelay 44 opens its switches 44-1 (circuit F) and 442 (circuit L) and closes switch 443 (circuit J). The operation of the switches 442 and 44-3 is ineffective at this time in the sequence and their function will be described later.

VVhenthe switch 4491 is opened, thecircuit-0t the operating coil cf: the relay 42 (circuit F) is opened to permit this relay to return to its tie-energizedposition, in which its switches 421 and 42.2 are-open. The

ings 4A of the dynamo-electric machine 4 from the" circuit 1. through the auto-tr ns. tor-men 8;: Che ante transtormer 8 ser as to .reduce the potential which is applied to the machine 4 during the starting period thereof. During this period, a field-magnet winding 4-13 of the machine 4 is disconnected from its energizing circuit by'a switch -1 of a field-magnet winding contactor 45, the operating coil of which is shown in circuit J. The operating coil of the contactor is deenergized until later in the sequence. A second switch 45-2 of the contactor 45, that is closed when the operating coil of the con tactor is tie-energized, closes a shunting circuit for the field-magnet winding 4B, comprising a resistor 46 and the operating coil of an inductive relay 47.

Since the fieldmagnet winding of the machine4 is shunted by a resistor and is not energized from an external source when the starting circuit interrupter 7 is closed, the

machine 4 starts to operate as an induction motor and drives the direct-current machine 5 by means of the shaft 6. At this time, however, there is no load on the direct-current machine and, consequently, the alternatingcurrent machine 4 increases in speed until it approaches synchronous speed. Until approximately synchronous speed is reached, the current that is induced in the field-magnet winding 4-13 from the armature windings 4-A traverses the operating coil of the relay 47 and holds the switch 47 1 (circuit J) of this relay open to preclude energization of the operating coil of the contactor 45. lVhen the speed of the machine approaches synchronism, however, the current that is induced in its field-magnet winding falls to a value that is insuiiicient to maintain the switch 471 of the relay 47 open. This switch therefore closes to connect'one terminal of the operating coil of the contactor 45 to the control conductor 2A.

Vhen energy is supplied to the armature windings 4A of the alternating-current machine 4, due to the closing of the starting circuit interrupter 7, an alternating-current reverseenergy relay 48 (Fig. 1) opens its switch 48-1 (circuit U) and closes its switch 4S2 (circuit U). The switch 481 when closed, close-circuits the operating coil of an auxiliary'relay 49 (circuit U) to preclude energization thereof. When the switch 481 is open, however, this close-circuit is removed to permit energization of the operating coil 1 the relay 49. The switch 48-2 is con nected in series with the operating coil of the relay 49 to establish an energizing circuit therefor when this switch is closed. 7

One terminal of the operating coil of relay 49 is connected through a resistor 50 and a conductor 51 to one terminal of the direct current dynamo-electric machine 5. As the speed of the machine 5 increases, due to the operating of the alternating-current ma- 'when the operating coil of this relay was energized simultaneously with-the energization of the auxiliary mastercontrol relay 34 (circuits D' and D--1 Whenthe operating coil of the relay 49 is energized, as described above, this relay opens a switch 49-1 (circuit V) and closes switches 49 2 (circuit U)- and 493 (circuit J1).

The function of the switch 491 will be de scribed later. The switch 492 is connected in parallel relation to the switch 48-2 to maintain a holding circuit for the operating coil of the relay 49. The closing of the switch 49'3 completes the energizingcircuit of the operating coil of the eontactor 45, (circuit J to effect opening of the switch 452 and closing of the switches 451 and 453, which have been previously described. Another switch 45 -4 (Fig. 1) which will be described later, is also closed when the operating coil of the contactor 45 is energized. -When'the switch 45-2 is opened, the circuit shunting the field-magnet winding4B of the alternating-current machine 4 is opened and when'the switch 451 is closed, the winding 4B is connected between the terminals of the directcurrent machine 5. This circuit extends from conductor 51 through switch 451, field-magnet winding 4B, regulating'resistor 52 and the operating coil of a field-current relay 57 to the conductor 3 of the direct-current system. The field-magnet winding 4B is thereupon energized from the direct-current ma chine .5 and causes the alternating-current machine 4 to come into-synchronism and to operate as'a synchronous motor.

A time-delay transfer and Voltage relay 53 is connected through a resistor 54 to the secondary winding of a potential transformer 55, the primary windingof which is connected across one phase of the alternating-current circuit 1. Relay 53 is provided with switches 53'1 and 532 (circuits K and V-21, respectively). The switches '531 and 532 are adapted to be maintained open as long as the voltage impressed upon the operating coil of the relay 53 exceeds a predetermined value, such as a value corresponding to of nor mal voltage on the alternating eurrent .circuit '1. WVhen the auxiliary switch 45-4of the contactc-r 45 is closed, due to the actuation of the contactor to its closed. position; the: 01%

crating coil of the relay 58- is c'lose-circuited through the switch 45. 4. and an auxiliary switch 9-2-ct therunning circuit interrupter 9,:that is'closed when the interrupter?) is open. Sincethe circuit interrupter 9 is open when the :switcl1- l l is'closed, switches 53--' l=a n(l 53 -2 are permitted to close. Glosing of switch53+-2 (circuit V -+211) inefffOQillNQ at this time because switch 4 which islconnected in seriesitherewith isopen,

current." 'llhus the relay 75 7 closes. its switch ST- 1 very soon atter ,the contact-or switch +1 is .closedto connect'the field-magnet :wriuidingetB hetweenlthe"terminals of the di root-current machined it Thus the operating, COllzOff thetranster relay 41-33 (circuit K), is energized as soon as'the alternating:current machine 4: has begun to operate as :a synchronousunotoiuand the cur.- rent traaersing'itsitieldunagnet Windinghas attained a predetermined ,value. 7 Then the oneratingycoih off the tran ster relay- L8 is enernzed. this relay pens tlsi w tch; 1 3- 1 (ci cuit F), which has been previously described,

and closes switches 43%.? (circuit I),

(circuit L) and 43,--,4 (circuit M 4). The switch 4-3-1; completes {a holding circu t for the operating coil oftherelaylfi to ma ntain energizationof the'coil ofthis relay aslong as the cimtrelconductor 2Aj jis energized from the conductor 2 of the ,direct cu1u'en-t system.

)VhentheswitchA3-2 is closed, acircuit is completed forenergizing a. tripping coil .71?) (circuit 1) toiythe startinglcircuit nterrupter 7. The circuit eaten'ds from the conductor 20f the direct-current system through switch 43-2, tripping coil TB and an auxiliary switch 7-2 to conductor? ottheidirec't- ,currentsystein. As soon as the tripp ng CQl'l (7B energized, the starting circuit :interrl dter 7 is opened to disconnect the alternat fin -current machine 4 i tr oin the auto transfor er 8 and to disccnnect the auto-trans: dormer 8Itrom the alternating-current circuit 1. hen the circuit interrupter 7 opens, its

auxiliaryiswitch 7- 2 (circuit 1) is opened to decnergize theitripping coil 7 B. y

Tillie-n therircuit interrupter 7' is opened, anauxiliary switch 7+3, (circuit L) closes to complete a circuit for energizing the top crating coilof therunning circuit interrupter 56-3 (circuit M),

control relay 56. This circuit extends from control eonductorQA through theswitch'? the coil of the relay 55, an auxiliary switch 93 of the running circuit interrupter 59,

switch 4&2 oftthewutcfi relayie l, which-is new de-ene1-gizecl',ancl switch .of the transfer relay as to the conductor 3v Oif the directrcurrent system. The -relaiy. 56 there- .uponvopens its switch 561:1 (eircuihGw-L) andcloses switches 56-2 (circuit L) and The switch 56.-2;is' connected in parallel relation to the auxiliary switch '9'3, of the circuit interrupt er- 9 and serves-to ,maintain a holding ,lcir'cu-it for ,the

operating coil ofthe relay )6 after the circuit interrupter-119 is closed. e

WVhen the switch 56 -3 is-closed, aici-rcuit is completed for energizing :t-he closing icoil 9A (circuit M) of the running circuit in-teruupter 19." The-armature windings {LA 'ozt' the alternating current ,Inaclnne 4: are thereupon energized directly i lQlll the ,aiternatiiigicirr- I-GlllLCl'l-Cllll? l. Atthesaunei'ti nethatthe closing coil 9A isener'gized the-time -rdeliay 'CUMOIJLE relay 44 is again energized; The energizing circuit Moat this relay new ieigtendstroin the conductor 2 01"- the directecurrent uc'ircuit through the switelhtG-ii (circuit M) ,of {the control relay 56 which: has ,been ipreuiously de'scriloed, the switcheii ak @(OlIlC1tlllhI\/L+ill) lot the transter relay A3 which has. also been, de-

scribed, .a conductor 9,18,;and the coil-riot the relay 1 (circuit (Eh-.12) ,to ithelcnnductorx 3 of the direct-current circurtl The .saultch ,5 t5'1 (circuit 1 can) iott the control relay ,56

is new open an d serves toqprecludeenergizetien oi the cloeingcorl (7A; otthe starting Q117- icuitiinternupter 7 at this :tin'ie.

elap'ied after the-opera-tingcoil 0t the tiniedelay :cut-olhrelayddi is energized, this relay cuit J), 'llhe opening the switch 44 (circuit F) iSJIljOW inenectiue since this eircuit ,isgalready openbecause the .sivrtchABel otthew-transfer relay A3 ;is .open; 1v The closing of the switch 44%3 isyalsoineffective. at this The} opening of the 5 switch iet ln'2 circuit .L)

is effective,- however, to interrupt the? energizing circuit of the :(control' relay 15.6: Tzhis relay thereuponopens its SWltClIQS EGTQE (cirswitch 56'1 (circuit (G 1;). Theopenlin-g of thc switch 56'2"interrupts.the holding circuitot'ithe operatingzcoil of the relay circui1t L) and ,tlievopening of theuswi t =l 563 interrupts thewen'ergizing circuits tor the'closinglcoil 9A.(circu it:h/I) oft the runnin circuit interrupterzi) .andlthe operating coil or" the cut-oil relay '44-. (circuit (ll- 41). During the time required v:tor the relayed to operate the -circ-uit interrupter .9 was closediand' latched cglosedrso that energize the time and its tunction awl lilbe descrihetlllater.

cuit and 56+ 8 (circuit W11) andljcloses-its tion of its closing coil 9A is no longer required. From the above descriptlon it will be seen that I utilize only one time-delay cut- 'ofli relay for'eifecting de-energization of the 'machine to its circuit to supply energy thereto will now be described.

The circuit interrupter 9,in closing, opens auxiliary switches 9l (circuit 13-5), 92 (Fig. 1), 93 (circuit L), 94I (circuit B54) and 95 (circuit X), and closes auxiliary switches 96 (circuit B'il), 97 (circuit B'54), 98

(circuit J), 99 (circuit 0) and 9 1O (circuit S). 'Opening of switch 91 is ineffective because theswit-ch -2 (circuit B.54) maintains a holding circuit for the operating coil of the relay 35' (circuit B). Opening of the switch 92 (Fig. 1) interrupts the short-circuit between the terminals of the relay 53 and permits this relay to become operative, as will be described later.

Opening of the switch 9-3 (circuit L) precludes re-energization oi the operating coil of the control relay 56 when the relay i l returns-to its tie-energized.position to close its switch. 44;2. The function of the remaining auxiliary switches of the circuit interrupter 9 will be apparent at later points in the sequence of operation of the'system'.

When the auxiliary control relay 40' (circuit E) was energized in response to the closing of the switch 34-3 (circuit C) of the auxiliary master relay 34 (circuit D) as pre viously described, the relay 4O closed, in addition to-switch 401 (circuit F), which has been described, two switches 402 and 403, which are-illustrated in Fig. 2 between a direct-current voltage'regulator 58 and a re- .versible:rheostat-operating motor 60. The

motor 60 isalso adapted to be connected to an alternati-ngcurrent frequency regulator 61 throughtwo switches 62-1 and 622 of an inversion auxiliary control relay 62 (circuit V-2) which will be described later. At this point in the sequence the operating coil of the relay 62 is de-energizedto permit the switches 621 and 622 to remain open.

The motor 60 is therefore controlledonly by the direct-current voltage regulator 58 through the switches 402 and 403, and is disconnected from the frequency regulator 61.

The direct-current voltage regulator 58 is preferably of the type shown and described in 'my co-pending application for voltage regulator systems, Serial. No. 584,613,

filed August 28, 1922, and assigned to the WVestinghouse Electric and Manufacturing Company. This regulator comprises three elements, 58A, 58B and 58C, each of which is provided with a balance-arm and a pair of contact members at each end thereof that are adapted to be engaged selectively, depending upon which way the balance-arm is tilted.

The element 58A is a Voltage-balancing element 1 comprising two opposing coils which act upon core members secured to the respective extremities of the balance-arm. Theleft-hand coil is connected between the conductors 2 and 3 of the main direct-current circuit and the right-hand coil is connected between the conductors 3 and 51, or, in other -words, between the terminals of the directcurrent machine 5.

The two coils of the element 58A are of equal numbers of ampereturns and are so disposed that, whenequal voltages are applied thereto, they exertequal 'iorce's upon their respective core members,

with the result that the balance-arm of this element is in equilibrium. When the voltage between the conductors 2 and 3 of the directcurrent circuit is greater than that of the machine 5, however, the left hand coil of the element 58A overbalances the right-hand coil, thereby tilting the balance-arm to close the right-hand contact members of this element, and vice versa. The element 58A is also provided with two auxiliary switches 58L and 58B, the purpose and circuitconneetions of which Will be hereinafter described. These switches are closed selectively, depending upon which way the balance-arm of this element of the regulator is tilted. I 1

The element 58B of the voltage regulator 58 is a voltage-regulating element comprising a single coil connected between the conductors 2 and 3 of the directecurrent circuit and acting upon a core member' that is secured to the 'left-handend of the balance-arm'of this element. A tension spring acts upon the oppositeend of the balance-arm and is so calibrated that, when the voltage impressed upon thecoil of this element is less than the normal voltage desired between the conductors 2 and 3 or the direct-current circuit, the spring exerts agreater. force on the balancearm than does the coil, thereby tilting the balance-arm to close the lefthand contacts of this element. "Similarly, when the voltage between the conductors 2 and 3 is greater than that which is desired, the force of the coil is greater than that of the spring, and the balance-arm is tilted to close the right-hand contact members.

The third element 58C of the voltage'regulator 58 is a current-regulating element which is similar in structure to the voltageregulating element 5813. The coil of this element is connected in parallel relation to the interpole field-magnet winding 10 of the maichine15. Since the winding lOis connected in series with the armaturewindings oi the machine .5 the voltage between the :terminals thereof is directly proportional tothe amount of current traversing the armature windings. Thus, itwil-l beseen' that, when thiscurrent exceeds-a predetermined yalue, :the force 6X" er-ted by the coil of the current-regulating element 580 is greater than that .exertedby the spring of this element, and,;theretore, the lmlanre-a-ian is tilted to 161036 the right-hand contact .rnembiers- .Conlversely, when i the cure rent is: less than the predeterminedvalue, the balance-minis tilted inthe opposite direction to close the left-hand contact members of this element. The coil iand'spring. are so calihratedand arranged that thisipredetermined; value of current-his themaximum desirable yalue illO bepermittedato. traverse the arma ture windings of the lnachine; V a

' As soonua-s the relay a closes its switches tOTQ ana=a0 e, bhedirect-current voltage regulator v58wbegins:to control the operation cxhthe .-rheosta=t-,operatimg motor. .60. ;The first operation of the voltage regulator 58 is to balance the noltageiot the machine .5 with the uoltageaoi (the direct currentcircuit. This is accomplished by the voltage-balancing element; 58A, whicl'i is ie-ifective by reason of the fact that: the direct-current circuit interruipterQl has not yet been closed, and an auxiliary switch ;2'l.:7 thereoiythat is closed when the icircuitintenrupter 21 is open, 18 connected in series inwtheicircuit-extending from the upper terminal of the machine 5 through the cond-uetorx5l to the balance-arm otithe element 58A. The voltage-regulating element 58B and thecurrent-regulating lelement 58C of the regulator 58 are ineffective until the circuit interrupter 21 :isclosed, by reason of the fact that the circuit extending to the balance-armsthereof includes an auxiliary switch 21-8 of thecircuit interrupter Qlthatis olosedonly .when that circuit interrupter is closed. j Ashas been explained .previously, the volt age-balancing element 58A; closes its right han d contact members when the voltage between-the conductors 2 and 8 otthe directcurrentcircuit is'greater than that of the machine 5, and closes its left-hand contactmenn bers when thevoltage of the machine 5 is greater than that between the conductors 2 and 3. Therefore, until the voltage of. the machine 5has built up to aval'ue equal to that of the direct-current circuit,tl1e right-hand contact members of the element 5813 are closed to connect the armature member and the'right-hand field-magnet winding otthe reversible rheostat-operating motor 60 in series between theternnnal's of the machine 5. This circuit eXtends irom-the upper ter minal of the machine 5, through the conductor 51, switch Q1T balance-'arm and 'rlghthand contact members of voltage-balancing masseuse element 58A,,switch ie-e2, right-hand field magnet winding and armature member oi motor 160, and vconductor 3'to the lower ter- "minal oi machine 5. The right-hand field magnet winding or motor 60 is so disposed with respect to the armature member that, when the motor .is energized in this way, it turns ina direction. to decrease the effectiveness of a (resistor 63 that is connected in circuit with the shunt field-magnet winding 5A of the-iniiachine The excitation of the machine-5 is, therefore, increased to insite direction to open the righthand contact members and to close the left-hand contact members of this element. The motor 601s then energized by a circuit extending. trom the upper terminal of the machine 5 through 1 F" t Y P i ionuuctor ol, switch 2l(, balance-arm and lett-hand contact members otelement 58A switch LO- 3 lei't-hand' held-magnet winding and armature member otmotor G0,, and conductor 23 to the lower terminal ofmachine 5.

The lelt hand field-m agnet windingiofimotor' (30 is so disposed with respect to the armature member that,'when the motor is energized in this waypit turns'inadirection to increase the oiliectiyeness oi. thermistor-163', thereby decreasing the voltage generated by the machine 5. Thus,;it mute seen that ithe'voltage-balancing element 58A controls the motor 601 0 vary the CITGCUVODGSS of the resistor 632 until the voltage of the vmachine 5 is exactly equal to that of the directrcurrent circuit. I

Until. this balanced condition is attained,

the twoauxiliary switches 58-R and 58-L,

ofitheyoltage balancingelement 58A, the circuit connections ofwhich are shown in circuit P, are alternately closed toenergize the operatingcoil ofa time-delay relay G l (cir- This relay is provided with a switch 6l-1 (circuit 53) that is adapted to be closed after the operating-coil ofthe relay 6% has been de-energized tor a predetermined inter- 58A is operating either to raise or to lower the voltage of the machine 5, and-permit closingof thiss witch only after the'voltage ot the machine 5 has been balanced with the voltage IUD otthe direct current circuit fora predetermined interval of time. p

An auxiliary switch 7--4l of the starting circuit interrupter 7 that is closed when the interrupter '7 is closed, and a switch 57-2 of the. field-current relay 5. that is closed ween the relay 5? is not energized to a predetermined degree, are each connected in parallel relation to the switches 58R and 5S-L (circuit 1 These switches preclude de-energization of the operating coil of the relay 6 1 and consequent closing of the switch Cir previously described.

6at1 while the starting interrupter 7 is closed and while the current traversing the lielduuagnet winding an of the machine 4- is below a predetermined value, respectively.

Thus when the circuit interrupter 7 is open,

the current traversing the field-magnet winding .13 is above a predetermined value, and the voltage of the machine 5 has been balanced with that'ot the direct-current circuit close a switch 6G1 (circuit B) when the voltage of the machine 5 builds up with the correct polarity relative to the polarity of the direct-current circuit. This relay affords protection against the remote possibility or the machine 5 being connected to the directcurrent circuit 'with its polarity reversed. )Vhenthe switrh G6-1 is closed, a voltage responsive relay 67 (circuit R) is connected between the terminals of the machine 5. The circuit of the operating coil of the relay 67 extends through the switch 391 (circuit of the control relay '39 which has been It the voltage of the machine'5 is above a predetermined value, such as, for example, of normal voltage, the relay 67 ellects closing 0t its switch 6'? -1 (circuit S). The operating coil or the relay 65 (circuit S) is now energized from the machine 5 through the circuit extending from the conductor 51, through the auxiliary switch 910 of the running circuit interrupter 9, an. auxiliary switch 211 of thcdire ct-current circuit in terrupter 21 (Fig. 2), a switch 68*1 of a time-delay cut-oil relay 68 (circuit T -1), switch (n+1 of the time delay relay c4, switch 671 of the voltage-responsive relay 67, and switch 391 of the control relay 39 to the conductor 3 of the direct-current cireuit. The relay 65 thereupon closes its two switches 65-1 and 652 (circuits S and T,

V respectively).

control relay 65.

The switch 651 so shunts the auxiliary switch 21-1 (circuit S) of the circuit interrupter 21 as to maintain energization of the operating. coil of the relay 65 after the interrupter 21 isclosed. The switch 652 completes a circuit for energizing the closing coil 21A (circuit T) of the circuit interrupter 21, and torenergizing the operatingcoil of the time-delay cut-off relay 68 (circuit T-1).

The circuit interrupter 21 is closed in response to'the energization of its closing coil 21A, and is latched in its closed position. The

cut-ofi relay 68 opens its switch 681 (circuit S) alter a predetermined interval of time to de-energizethe operating coil of the The switches 65l and 652 are then permitted to open. Opening of the switch 651 interrupts the holding circuit for the operating coil of the relay 65 (circuit S) and opening of the switch 652 interruptsthe energizing circuit for the closing coil 21A (circuit- T) of the interrupter 21 and fertile operatingcoil of the cut-oil relay 68 (circuit T-l). The interrupter 21 is now latched in its closed position and all of its controlling apparatus is de-energized.

The operation of starting and connecting the machines 4 and 5 to their respective circuits to translate alternating-current energy into direct-current energy under normal condition is now completed. The machines continue to operate in this manner as longas there is a sufiicient'demand for energy upon the direct-current circuit.- During such opcurrent-regulating element 58C operates to maintain the current output of the machine at'the-maximum permissible value, and to vary its voltagein accordance therewith.

VVhenthe circuit interrupter 21 was closed, its auxiliaryswitch 217 was opened to disconnect the balance-arm of the voltage-balancing, element 58A from the conductor 51, and the auxiliary switch 218 was closed to connect the balance-arm of the current-regulating element 58C to the conductor 51. The

element 58A was thus rendered ineffective,

and the elements 58B and 580 were rendered effective upon closing of the circuit interrupter 21. As previously set fortlnwhen the current traversing the machine 5 is less than the maximum desired-value, the-left-hand contact members of the current-regulating element 58G remain closed. These contact memrent circuit. The energizing circuit for the clutch coil 30A extends from the conductor 2,

through switches 81-1 and 321, coil 30A,

switch 351 of the master control relay 35, and switches 691 and 96 to conductor 3.

Since the clutch coil 30A is now energized the switch 301 is not closed, but switches 30-2 (circuit B-52) and 303 (circuit O5) are actuated toward their respective closed positions. The time setting of the switch 303 is considerably less than that of the switch 30-42 but its closing at this time is ineffective, as will be described later. If the load demand on the machine l increases to a value greater than the value at which the underload relay 69 is adjusted to close its switch 69'1 before the time-delay relay 80 has closed its switch 302, this switch is permitted to return immediately to its open position. Thus the condition of under-load must persist continuously for the time interval for which the switch 30,-2 is adjusted to operate in order to effect automatic c isccnnection of the machines l and 5 from their circuits.

WVhen the switch 30- 2 is closed in response to this condition the operating coil of the masster control relay 35 (circuit B-5) is shortcircuited thereby, and the switches 35l (circuit B 3), 352 (circuit 1354i), anc 35-3 (circuit D) are permitted to open and the switch 35-4 (circuit V21) is permitted to close, The function of the switch 35% will he described later. Opening of the switch 35l de-energizes the clutch coil 30A of the time delay relay (circuit B3) and permits the switch 302 to return to its original position. Opening of the switch 352 interrupts the holding circuit for the operating coil of the master relay 85, and precludes immediate re-energiz ation thereof when the short-circuit between its terminals is removed due to the opening of the switch 302. Opening of the switch 35-3 interrupts the energizing circuit for the operating coil of the auxiliary master control. relay 34 (circuit D) and per- "mits this relay to open its switches 3 l3 (circuit C) and Si k-4: (circuit AA) and to close its switches 3 l-1 (circuit B) and 342 (circuit B52). The operating coil of the control relay 39 (circuit D-1) is also de-energized when the switch 35-3 is opened, and

this relay thereupon opens its switch 39- -1 (circuit S) and closes its switch 392 (circuit O).

The control conductor 2A is not immediate- 2 lydisconnected from the conductor 9. when the switch 34-8 (circuit C) is opened, for their switch is shunted. by an auxiliary switch 212 of the direct-current circuit interrupter 21 that is closed when the interrupter 21is closed. Thus the conductor 2A is energized from the conductor 2 as long as the circuit interrupter 21 is closed. The interrupter 21 is opened in response to the opening of the switch 391 (circuit S), because a no-voltage tripping coil 21C (circuit S1) of the interrupter 21 is de-energized thereby.

When the interrupter 21 opens the auxiliary switch 212 (circuit C) also opens to disconnect the conductor 2A from the conductor 2 and thereby to de-energi'ze all of the control apparatus that is connected to the conductor 2A. This iiicludes a no-voltage tripping coil 9O (cir cuit N) of the running circuit interrupter 9, which causes the interrupter 9 to open todisconnect the machine 4 from the circuit 1. The encrgization of the conductor 2A through the auxiliary switch 21-2 until the interrupter 2l opens insures the disconnection of the machine 5 from the direct-current circuit prior to the disconnection of the machine .4: from the alternating-currentcircuit, thereby precluding a reversal in the direction of the flow of energy between the circuits.

As the machines gradually come to rest, the voltage generated by the machine 5 decreases gradually to zero and the control apparatus that were energized therefrom return to their tie-energized positions. All of the apparatusin the station is now in the same condition that was originally assumed, and is again ready to respond to similar conditions in the same manner as described above.

The operation of the'machines may be stopped automaticallyin response to predetermined conditions other than a condition of under-load in the manner described above. Various protective devices such as the alternating-current thermal relay 33 (Fig. l) and a phase-balance current relay 71 (Fig. 1) may be provided with switches such as 33-2 (circuit B51) and 711 (circuit.

l354), respectively, that short-circuit the operating coil of the master relay 85 (circuit B-5) to stop the operation of the machines in the same manner that they are stopped in response to the closing of the switch 30-2 (circuit B.52) in response to sustained under-load. The switch 7ll is connected in series with an auxiliary switch 97 (circuit B54) between the terminals of the master relay 35 so that unbalanced currents'inthe several phases of the armature windings LA of the machine 4 cause the coil of the relay 35 to be short-circuited only when the run: ning circuit interrupter 9 is closed.

If such an unbalanced condition occurs while the machine 4 is being started, it is an indication of internal trouble in the machine, and it is desired that the machine be locked out of service until an inspection thereof has been made. This is accomplished by means of the lock-out relay 32 (circuit C). If the phase-balance relay'71 closes its switch while the machine is starting, short-circuiting of switch 9-.Z (circuit B5a) is open, but since another auxiliary switch 9- (circuit C-2) of the running circuitinterrupter 9 is closed, the operating coil of the look-out relay 32 (circuit C) is energized.

The circuit for energizing the relay 32 e2;- tends from conductor 2 of the direct-current circuit through switch (circuit C) of the auxiliary master relay 34, a closed switch 'T21 of a relay 72 (circuit V22) to be described later, coil of relay 32, switch 9% (circuit C 2), and switches 71-1 and 2 (circuit B5et) to conductor 3. The relay thereupon opens its switches 321 (circuit B) and (circuit B.5) which latch in their open positions and so remain until they are reset manually by an attendant. The switches 32l and 322 open the circuits of the time'delay relay 3O (circuit B) and the master relay 35 (circuit 13-5) and thereby entirely preclude further operation of the machines in the station until the relay 82 is reset.

Other relays such as a direct-current thermal relay 73 (F ig. 2), and an alternating current short-circuit relay 74 (F ig. 1) may be provided with switches such as 7 3-1 (circuit C3) and 7 l1 (circuit C-4) which are also adapted to energize the lookout relay 32 when they are closed in response to predetermined abnormal conditions. The switch (circuit of the time-delay relay 30 is connected in series with an auxiliary switch 'T-b of the starting circuit interrupter 7 so that if the switch 30-3 is closed while the interrupter 7 is closed, the look-out relay 32 will be energized. Tlfhis'affords protection against the machine l running for an abnormal length of time on the starting connections, which is an indication of trouble, within the station.

i This protection is obtained by providing an auxiliary switch 76 (circuit B3) of the interrupter 7 that-causes the motor winding 30 and the clutch winding 30A of the timedelay relay to be energized as soon as the interrupter 7 is closed. If the transfer from. starting to running connections is effected within a normal period of time, the interrupter 7 will be opened before the switch 303 is closed. The coils of the relay 30 are then de-energized because of the opening of the auxiliary switch 7-6 (circuit B-.3) and that relay: returns to its original position. If the interrupter 7 remains closed for an abnormal length of time, such as two minutes, however, the switch 303 (circuit C 5) isclosed and causes the apparatus to be locked out of service as described above. When the apparatus is locked out during the starting period of the machine 4 the startingcircuit interrupter '4' is tripped by a no-voltage trip coil 7C (circuit H) that is de-energized when the conductor 2A is disconnected from the, conducton2 by'the opening of the switch conditions will cause the apparatus to be stopped, but will permit restarting thereof when conditions again become normal. Occurrence of a permanent fault, however, will cause the apparatus to be stopped immediately and will preclude re-starting thereof untilthe station has been visited by an attendant who resets the lock-out relay after remedying the fault which caused the operation thereof. i

The apparatus in the station may also be manually stopped from the control station 23 (Fig. 1). If it is desired to stop the apparatus immediately at any time, but to permit automatic re-st-arting, thereof, the pushbutton' 2% is depressed. This connects the control conductor 28 directly to the conductor 2 of the direct-current circuit, which causes the operating coil of the stopping relay 86 (circuit AA) to be energized. The energizing circuit for this relay may be traced from conductor 2 of the direct-current circuit, through switch 24 in the control station, conductor 28, coil of relay 36, and switch 34 of auxiliary master relay S4, to conductor 3.

When the coil of the relay 36 is energized, this relay opens its switches 36-1' (circuit B-5) and 362 (circuit Afr-53) and closes its switch 3 63 (circuit AA). The latter switch so shunts the switch 3l4 (circuit AA) as to maintain energization'of the operating coil of the relay 36 after the relay 34' opens its, switch 344, as long as the pusl1- button switch 24 is kept depressed. The switch 36-1 (circuit B-5) opens the circult of the master relay 35 and thereby causes the operation of the machines to stop, as previously described; The opening of the switch 36-2 (circuit AA3 prevents the establishment of a short-circuit between the conductors 2 and 3 of the direct-current circuit, which otherwise might occur under certain conditions.

As soon as the switch 24 is released, the

circuit of the coil of the relay 36 (circuit- AA.)

is broken, so that this relay again opens its switch. 36.3 circuit AA) and closes its switches 36-1 (circuit B5). and 362 circuit AA3). Automatic or manual starting of the apparatus may now take place at any time. If it, is desired to preclude restarting of the apparatus the knife-switch 26 at the to take energy from the alternating-current circuit and to supply energy to the direct-cur rent circuit, the normal auxiliary master control relay 34 (circuit D) will be energized, and its switch 3 1-4: (circuit AA) will be closed. The operating coil of the stopping relay 36 (circuit AA) will thenbe energized as previously described and its switch 36-3 will maintain a holding circuit therefor as long as the switch. 26 is closed in its upper position and operation of the apparatus will be precluded because the switch 36-1 (circuit 13-5) will be maintained open.

Likewise, if the apparatus is operating in the inverted manner, so-called, to take energy from the direct-current circuit and to supply energy to the -alternating-current circuit, a switch 72-2 (circuit AA) of the auxiliary inversion relay 72 circuit V-22), which will be described later, will be closed. The switch 72-2 shunts the switches 34-42 and 36-3 (circuit AA) and the operating coil'of the stopping relay 36 is energized in the same manner though the switch 3-4-4 were closed. I

If the switch 26 is closed in its upper position while the machines 4 and 5 are not operating, the switches 34-4, 36-3, and 72-2 (circuit AA) will all be open, and the coil of the stopping relay will not be energized until the apparatus attempts to start either normally or inverted. When such an attempt to start is made, either the switch 34-4 or 72-2 will be closed, and the stopping relay 36 will then function as before to preclude operation of theap iiaratus until the switch 26 has been moved from its upper position and either a manual or an automatic starting indication has been given. I

The apparatus may be started manually from the control station 23 by closing the push-button switch 25, provided the switch 26 is closed in its lower position and starting is not precluded by any abnormal conditions in the power station. The circuit for manual starting extends from the conductor 3 of the direct-current circuit, through the push-but-- ton switch 25 and the knife switch 26 in its lower position at the control station 23, over the control conductor 28, through a resistor and switch 36-2 (circuit Ail-3) through a switch 76-1 (circuit 13-52) of-an inversion starting control relay 7 6 (circuit V-21) to be described later, through a switch 34-2 (circuit 13-52) of the normal auxiliary master control relay 3% (circuit D), through the operating coil of the normal master control relay 35 (circuit 13-5) and thence through resistor 37 and switches 36-1, 32-

2, 32-1 and 31-1 (circuits B-5 and B), as previously described for automatic starting, to the conductor 2 of the direct-current circuit. The operating coil of the normal ductor 3 of the direct-current circuit.

master control relay 35 is thus energized from the direct-current circuit, and the remainder of the automatic control apparatus functions as previously described to start the machines 1 and 5 and to connect them to their respective power circuits.

The control conductor 28 has one other function, namely, to energize the indicating device 27 in the control station 23, to indicate whether or not the machines in the power station are operating. lVhen the circuit interrupter 21 is closed to connect the machine '5 to the direct-current circuit, an auxiliary switch 21-3 (circuit AA-l) is closed to connect a resistor 78 in series with the indicating device 27 across the direct-current circuit. This circuit extends from the conductor 2 of the direct-current circuit, through aresistor 99 and the indicating device 27 (Fig. 1) over the control conductor 28, and through the resistor 78 and switch 21-3 (circuit AA-l) to the con The device 27 may beeither an ammeter or a voltmeter, properly calibrated, and when it is traversed by current of a predetermined value, depending upon the predetermined resistance of the circuit described above, its pointer will assume a predetermined position which will correspond to a mark on the dial indicating that one power unit is connected between the power circuits in the main station.

Where there are more power units than one in the main station, additional circuits such as AA-2 will be provided in parallel relation to the circuit AA-l. Each additional circuit of this sort will comprise a resistor, such as 178, and an auxiliary switch, such as 121-3, of the main direct-current circuit interrupter of the corresponding unit. Thus, as each additional unit goes into service, another resistor will automatically be connected in parallel relation to the resistor 78, thereby decreasing the total resistance of the circuit of the indicating device 27. In other words, the resistance of that circuit is varied according to the number of units operating, and since the deflection of the indicating device 27 varies according to the current traversing, and hence the resistance of its circuit, this device will indicate just how many units are opera tively connected to the direct-current circuit.

The foregoing description covers in detail the various features of operation of the sys tem embodying my invention, assuming that energy is available at all times from the alternating-current circuit 1. As stated before, however, if the voltage of the circuit 1 should fail it is desired that the direct-current machine 5 shall operate as a motor to drive the alternating-current machine 4 as a generator to supply energy to the circuit 1. This gives rise to the consideration of four more possible operating conditions, namely, 1) failure of both alternating-current and direct current :igsszuse voltageswhile the machines are operating normally; (2) failure o'f both alternatingcurrent and direct-current voltages while the machines are not operating; (3) failure or.

direct-current circuit to the alternating-current circuit, which is the reverse of normal operation. 'Undercondition (3) the machines will continue to io'perateandthedirection of energy traversal thereof will be reversed without stopping and rel-starting the machines. Therefore, we have to consider inverted starting and operation of the machines from stand-still, and inversion whilethe machines are runnin These conditions will be described in the order named.

Let us assume any one of conditions (1), (2) and (4), above, when direct-ciu'rent energy is available at the power station and alternating-current energy is not available, and

the machines are not'operating. NVhen the alternating-current voltage fails, the relay 53 (Fig. 1) closes its switches 53-1 (circuit K) and 532 (circuit V2-1). Switch 582, whenclosed, completes acircuit for energizing theoperating coils of the. inversion starting control relay 7 6 (circuitV-21),andthe inversion auxiliary starting control relay 72 (circuit V 22). This circuit may be traced from the conductor2 of thedirectcurrent circuit through the switches 31-3-1, 32 1, 32-2 and 36-1 (circuits B and B5), which havealready beende'scribed, over a conductor 7 9, through a switch 40 i (circuit V2). of the normal auxiliary control relay 4O (circuit which is now de-energized, thence over two parallel paths, one of which comprises a resistor 8Q and the operating coil of the relay 76 (circuit V-21), andthe other of which comprises theoperating coil of the relay 7 2 (circuit V 22), and thence through the switch 35.4ofthenor1nal master control relay 85 and the switch 53 -2 of thevoltageresponsive relay 53 to thecondnctor of the direct-currentcircuit. a 1

The relay" 76, when energized, opens switch 6-1(circuit B552). and closes switches ?6-2 (circuit L-1) {76- 3% circuit V'2l) and,76- 4: (circuit X); Therelay 72 simultaneously opens switch 72-1 (circultfl) and closesswitches 72-2 (circuit A A.) 723 an d 72%: (circuit 13 53) 7 2 -5 (circuit C-1),,and "T 2-+6 and 72-7 (circuit D). The switches 76 1, 72--1 and.72V-2 have already been described. The function of the remaining switches enumerated above will be described as theyrbecome effective in the sequence; Siv 1tch-764, when closed,;com-pletes a circuitforener izin the oieratin r coil of a direct-ciu'rentstarting con-tactoi" ck'introl reflay '81 (circuit: X). This circuit extends from-the conductor ofth'c direct-current circuit through an auxiliary switch 9-5 of the alternating-current running circuit interrupter 9, (3011 of relay 81 and switch ilkl to the conductor?) of the direct-current circuit. relay 81 thereupon closes its switch 81-1 (circuit Y) to conncct'theclosingcoil 18A of the direct-current starting contaetor-=18= (Fig. 2) across the direct-current circuit. The contactor 18 is then closed to connect the upper terminal of the machine 5"to the conductor 2 of the direct-current circuit'through the resistors 12, 13 and 14 and the series current relays15, 16and17.

The directcurrent machine 5 now receives energy "fromithe direct=current circuit over the circuit just described and begins, to operate as a motor. The current traversing the relays 15, '16 and 1'? isat' first great enough to cause these relays t0 open their respective switches 15- 1 (circuit 21), 16 1 (circuit ZZ)'and17 1 (circuitS); As the speedand hence the counter electroanotive force of the machine fifincreases, however, this current decreases to such .a v'alue that t-he'relay 15 is permitted to; close its switch'15 1:to cause the closing coil 19A (circuit'Z) of the resistance-shunting contactor 19 '(Fig."2)to he energized from the direct-current circuit. The contactor 19 thereupon closes" to short circuittherejsistor12f(Fig.i2). i V

The speed of tl'ie nachine 5 .now increases further untilzthe current traversing the re- 1 16 falls/to such a valuelthat the switch 16.1' is closed to effect energization of the closing eo'il20A (circuit Z-Z); of the contactor 20- (Fig. The contactor 20 th en closes to short-circuit the operating coil of the relay 15 and the resistor 13(Fig. As the current traversing the relay 17fdecreases to a value which permits this relay to closeits s Th; switch 39 1 (circuit S) of the control relay .39 (circuit'D-j-l is now closed because the operating coil of,thisrelay;was connected across 3 the direct-current circuit the closing of the switch 72+7 (circuit D)'of there lay "Z2 (circuit V22)previously'mentioned.

The

its

The switch 72-6 (circuit D) of the same relay closed simultaneously to short-circuit the operating coil of the normal master control relay 34, to preclude energization and actuation thereof. The switch 34-3 (circuit C) did not close, therefore, to connect the con ductor 2A tothe conductor 2, and connection betweenthe conductors is not efiected until the direct-current circuit interrupter 21 is closed to. close its auxiliary switch 21-2 (circuit C). y I

WVhen the machine 5 started to take energy from the direct-circuit through the circuit interrupter 21, current traversed the shunt 22( Fi in the reverse of normal direction, to cause a reverse-current relay 82 (Fig. 2) to open a switch 82-1 (circuit V) and to close a switch 82-2 (circuit V). Since the alternating-current reverse-energy relay 48 (Fig. 1) is tie-energized because the armature windings 4A of the machine 4 are open-circuited, the switch 48--1 (circuit U) of this relay is closed and the switch 48-2 (circuit U) is open. The operating coil of the relay 49 (circuit U) is therefore tie-energized and its switch 49-1 (circuit V) isclosed. Thus whenthe switch 82-2 is closed, the operating coil of the inversion master control relay 41 is completed from conductor 79, through resistor 83, coil of relay 41,.and switches 82-2 and 49-1 to conductor 3. The relay 41 thereupon opens its switch 41-1 (circuit E) and closes its switch 41-2 (circuit V).

Opening of the switch 41-1 precludes energization of the operating coil of the normal auxiliary control relay 40 (circuit E) and therefore its switch 40-4 (circuit V-2) remains closed, and its switches 40-1 (circuit F) and 40-2 and 40-3 (Fig. 2) remain open. Since the switch 40-1 is open the operating coil'of the relay 42 (circuit F) cannot be energized, the switch 42-2 (circuit G) remains open, and, consequently, the closing coil 7A of the alternating-current circuit interrupter 7 cannot be energized. The running lnter rupter 9 is closed, however, as will be described presently. V

The switch 41-2 of the inversion master relay 41 is connected in parallel relation to the switch 82-2 (circuit V) and maintains a holding circuit for the relay 41 after the switch 82-2 opens. This switch also completes theenergizing circuit of an auxiliary relay 84 (circuit V-1) and an inversion auxiliary control relay 62 (circuit V-2). The circuit of the relay 84 extends from conductor 79, through the coil of relay 84, and through switches 41-2 and 49-1 to conductor 3. The relay 84, when energized closes a switch 84-1 (circuit TV) to connect the closing coil 85A of a shunting contactor 85 (Fig. 2) across the direct-current circuit. The contactor 85 is thereupon closed to short-circuit the series field-magnet winding 11 of the machine 5 while it is operating as a motor.

through the switch 40-4 (circuit V-2 The circuit of the inversion auxiliary controlrelay 62 extends from the conductor 79, an auxiliary'switch 21-4 (circuit V2) of the circuit interrupter 21 (Fig. 2), coil of relay 62, and switches 41-2 and 49-1 to conductor 3. The relay 6 2 closes switches 62-1 and 62-2 (Fig. 2), previously mentioned, and 62-3 and 62-4 (Fig. 1) and opens switches 62-5 and 62-6 (Fig. '1). The

function of the switches, will be more fully described later. 7

The switch 76-2 (circuit L-l) of the inversion starting control relay 7 6 is connected in series with an auxiliary 7 switch 21-5 (circuit L-l) of the circuit interrupter 21 to effect energization of the-operating coil of the transfer relay 43 (circuit K) as soon as the interrupter 21 is closed. The alternating-current running circuit interrupter 9 (Fig. 1) is now closed, latched closed, and its closing coil tie-energized in. the same manner as described for normal starting of the apparatus.

When the interrupter 9 is closed its auxiliary switch 9-8 (circuit J) cooperates with switch 44-3 (circuit J of the time-delay cutoff relay 44 (circuit G-1), which remains closedfor an instant after the interrupter 9 is closed, to effect energization of the closing coil of the contactor 45 (circuit J). This contactor immediately opens its switch 45-2 '(Fig. 1) and closes its switches 45-1 (Fig. 1) and 45-3 (circuit J). Switch 45-2 opens the circuit shunting the field-magnet winding 4B of the machine 4 and switch 45- 1 connects the winding 4B across the termi Inals of the machine 5 to be excited from the direct-current circuit. Switch 45-3 so shunts switch 44-3 (circuit J.) of the cutoff relay 44 as to maintain energization of the closing'coil of the contactor 45 after the switch 44-3 is opened.

Auxiliary switch 9-9 (circuit 0) of the interrupter 9 connects the operating coil of an inversion auxiliary master control relay 86 (circuit 0-1) across the direct-current circuitwhen the interrupter 9 is closed. The relay 86 thereupon opens its switch 86-1 (circuit B-53) and closes its switch 86-2 (circuit 13-53). Until the interrupter 9 was closed the switch 86-1 co-operated with. switch 72-3 (circuit 13-53) of the invcrsi on auxiliary starting control relay 72 to shortcircuit the operating coil of the normal master control relay 35 (circuit 13-5), but this short-circuit is now broken and switch 86-2 co-operates with switch 72-4 (circuit 13-53) of the relay 7 2 to connect the operating coil of the relay 35 across the direct-current circuit. The relay 35 is thus energized and its switch 35-2 (circuit B-54) establishes a holding circuit for maintaining energization of the operating coil after the switch 72-4 is opened.

is broken by the opening of the 5% and the relays 34 and trols the rheostat Loperati motor through theswitches-62l and 62-2, this motor.bc ing disconnected from the direct-current voltage regulator58 because the switches i-O-2 and 4031are open. The frequency regulater 61 comprises a balance-arm and a pair otcontact members at each end thereof that are adapted-to be engaged selectively, depending upon which way the balance-ari'i'i is tilted. Two operating coils are provided ,whicliact upon core members secured to the respectiveextremities of the balance-arm. The circuit of the left-hand operatingvcoil comprisesareactor in series therewith, and the circuit of the r1ghthand coil comprises a similarly-conuected resistor. These two circuits are connected in parallel relation to each other audareenergized through. conductors 87 and 8S fromthe secondary winding of a potential transformer (Fig. 1), the primary winding ofwhich is connected across one phase of the circuit of the armature WlIlCllDgSAAJfi the altei'natingcurrent machine .4.

The potential transformer 89 is also, connected to the operating coil of an alternatingcurrentvoltage regulator 90 (Fig. 1) and to,

a, potential coil of the alternating-current reverse-energy relay 4S Fig. 1),the current coil of which is energized from one of thecurrent transformers 77. These current transformers also energize current coils in the thermal relay 33, the under-load relay 69, the

phase-balancerelay 71, and the short-circuit relay 74,.asshown. The functions otall ot these relays have been described previously.

Thefrequency regulator 61 is so construct ed that, when equal currents traverse. its two operating coils,its balance-arm in a bill? anced condition, but. when the current traversingthe left-hand coil exceeds that traversingthe right-hand coil, thelbalancearm is tilted to close the right-hand contact members, and vice versa- The reactor and the resistor that are connected in series with the respective coils are so chosen that the impedances of the two coil circuitsare equal at the desiredfrequency of the alternating-current circuit 1. Theret'ore,-when the machine lisgeneratingcvoltageat the desired frequency, equal currents will traverse the two coils of the frequency regulator 61, since. the circuits of these coils areenergizediin parallel relation to each other from the terminals: of the machine 4 through the transformer 89and the conductors 87 and 88. I

It the machine t is being driven at too great a speed, the frequency of the voltage generatedthereby is also too great, and the frequency regulator 61 must function to reduce the speed of the machine l. This is accomplished by reason of the fact that the impedance ofthe circuit of the left-hand coil of the regulator is greater than-at normal trequencyysince a reactor is connected there in, while the impedance-of thecircuitot the right-hand coil is substantially unchanged. The right-hand coil is, therefore, more strongly energized than is the left-hand coil and, asa result of this fact, the balancearm ot' the regulator is tilted to effect closing of the left-hand contact members. A circuit is thereby completed, extending from the upper terininalof the machine 5,through conductor 51, balance-arm and left-hand contact members of regulator 61 switch 621,right-' h and field-magnet winding and armature member of motor 60, and condu'ctorSto the.

lower terminal of machine 5.

'As previously stated, when the motor '60 is energized in this manner itoperates" to decrease theeffectiveness of the resistor68, thereby increasing theexcitation ot' the machine 5. Since the machinea5. is now operating as a direct-current-shunt motor, thistincrease in its excitation causes itsspeed tot decrease, and thetreq-uency'ot' the voltage generated byt /the machine 4;"is'correspondingly decreased. In like manner, when the frequency is too low, the energization of the left-handcoil of the regulator 61 is greater than that of the right-hand coil, and therighthand contact members of this regulator are thereupon closed to effect energization of the motor 60 through its left-handfield-magnet winding. l The excitation of the machine5 is thusdecreased and its speed correspondingly increased toetlect the proper increase in the frequency of the voltage generated by the machine 1. 'Thus, it will. be seen thatjywhile the machine 5 is operating as a motor to drive .then'iachine L t as a generator, the regulator 61 controls the speed of the machine5 through the agency of the motor60 and the resistor 63 to maintain'thefrequency of the voltage generated by the machine-4 at the predetermined desired value. 1 i I During inverted operation ofithe machines sand 5, it is necessary to-maintain' the inag nitu'de of'the voltage generated by the machined constant at a predtermined valuer-as well as'the. frequency of this voltage. This is accomplishd by the alternating-current 

